Rubber crawler

ABSTRACT

The present invention provides a rubber crawler used for a running unit of a vehicle for farm work, or civil engineering/construction work. Core bars are embedded with a constant spacing in a lengthwise direction of the rubber crawler without steel cords. A closed-loop opening is formed in each of left and right wing portions, which are of a rubber embedding portion of a core bar. The edge portions of the closed-loop openings of the adjacent core bars are fitted into fitting portions with a coupling body including the fitting portions in which both ends are opened in an inward direction. The edge portions are connected with each other at the coupling body to make the coupling body as a counter-tensile material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rubber crawler mainly used for arunning unit of construction or civil engineering machinery (hereinaftermerely referred to as vehicle). More particularly, the invention relatesto a rubber crawler which adopts a novel structure as a tensilereinforcement.

2. Description of the Related Art

In the structure of the rubber crawler used in the conventionalvehicles, as shown in FIG. 1, a core bar a which forms a running path ofa rotating wheel is embedded in a rubber b with a constant spacing in alengthwise direction of the rubber crawler, and steel cords d in a roware also embedded in the rubber in order to surround outsides of leftand right wing portions c of the core bar a to resist tensile forceapplied to the rubber crawler. A top surface of a projection ao formedin the core bar a becomes a running surface of the rotating wheel.Because relatively thin cord wires are twisted in the steel cord d, rustis generated due to moisture invading the rubber from the outside, andfinally breakage of steel cord d is not prevented from occurrence.

Japanese Patent Laid-Open Publication No. 2000-313371 is an example inwhich the steel cord is not used. As shown in FIG. 2, in the rubbercrawler of Japanese Patent Laid-Open Publication No. 2000-313371, rods fwhich corresponds to the left and right wing portions are used. Pairs ofthe rods f and f are inserted through blocks g and g from left and rightends of the rods f and f. Coupling links h and h are fitted into therods g and g. A row of the blocks g is arranged to be shifted regardingthe other row of the blocks g. The top surfaces of the blocks g as awhole become the running surface of the rotating wheel. The couplinglinks h and h are employed instead of a conventional steel cord.

In the rubber crawler of Japanese Patent Laid-Open Publication No.2000-313371, the rod f, the block g, and the coupling link h must beregularly combined. This demands careful assembly and the productionefficiency is questioned. The block g and the coupling link h are needto be assembled from the left and light sides of the rod f. This means agreat width of a work space. In addition, when the rod f, the block g,and the coupling link h are arranged at predetermined positions of amold of the rubber crawler after the assembly, the block g or thecoupling link h might disengage from the rod f. No space exists wherethe rod f is fitted into the block g or the coupling link h in the mold.These features show that the production efficiency is not good.Generally, dealing with the rod f by hand is not recommended. In thispoint, in the technology of Japanese Patent Laid-Open Publication No.2000-313371, manual handling of the rod f is indispensable for fittingthe rod f into the block g or the coupling link h from a widthwisedirection of the rod f. Such handling affects the adhesion of the rods fto the rubber.

SUMMARY OF THE INVENTION

The present invention differs from the conventional technology in thetechnical idea. The invention provides a novel structure of the rubbercrawler in which the steel cords are not used.

Further, the invention is mainly made in order to prevent the phenomenonof the steel cord breakage. The invention provides the rubber crawler inwhich the steel cords formed by twisting thin wires are not used.

A rubber crawler of the invention has core bars which are embedded withconstant spacing in a lengthwise direction of the rubber crawler. Therubber crawler further has following features. A pair of edge portionsis formed in each of left and right wing portions which are of a rubberembedding portion of a core bar. The edge portions of the adjacent corebars are coupled with each other by fitting the edge portions intoanother fitting portions with a coupling body including the fittingportions in which both ends are opened in an inward direction. In thisway, the coupling body can be a counter-tension portion.

With reference to a shape of the wing portion of the core bar, the pairof edge portions is made by forming a closed-loop opening in the leftand right wing portions. Alternatively, the pair of edge portions ismade by forming a tuning fork shape in the left and right wing portions.A cross section of the edge portion may have a substantially circularshape.

With reference to the coupling body, the coupling body includes thefitting portions in which both ends are opened in the inward direction,and appears to have a C-shape or an S-shape when viewed from a lateralface. The coupling body is made of metal or plastic.

With reference to a relationship between the coupling body and the edgeportion, a condition that L≧1.5 R and A/D≧0.7 may be used when a radiusof the cross section of the edge portion of the core bar is set to R, awidth of the edge portion is set to D, a length from the deepest portionof the fitting portion of the coupling portion to an end of the fittingportion is set to L, and a width of the coupling body is set to A.Another condition that A/B≧0.3 and A/C≧0.1 may be used when a lateralwidth of the wing portion of the core bar is set to B and a lateralwidth of the core bar is set to C.

With reference to the relationship between the pair of edge portions andthe rubber crawler, a condition that 0.7≧L₀/P≧0.4 may be used when acenter interval of the pair of edge portions is set to L₀ and a spacingof the rubber crawler is set to P.

With reference to the relationship between the coupling body embedded inthe rubber crawler and the rag, from the viewpoint of durability of therubber crawler, the rubber rags are preferably formed in an outersurface of the rubber crawler located at a position where the couplingbody is covered.

As a structure of the rubber crawler in which the coupling body isembedded, a recess A may be formed opposite an edge side in alongitudinal direction of the rubber crawler of the coupling body, on aninner radius side and/or an outer radius side of the rubber crawler. Therecess A may be through an inner surface to the outer surface of therubber crawler. The recess A may be formed along the edge portion in awidth direction with respect to the rubber crawler of the coupling body.

In consideration of winding resistance or the like, a recess B may beformed on an inside and/or an outside in a rubber elastic body out ofthe coupling body embedded in the width direction of the rubber crawler.The recess B may be formed on the inner radius side and/or the outerradius side of the rubber elastic body. The recesses B may be formed inline in the width direction of the rubber elastic body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an oblique perspective figure showing a structure of a rubbercrawler used for the conventional vehicle.

FIG. 2 is an oblique perspective figure of a core bar showing thestructure of the rubber crawler disclosed in Japanese Patent Laid-OpenPublication No. 2000-313371.

FIG. 3 is a plan view showing an inside of the core bar used for therubber crawler of the invention.

FIG. 4 is a front view showing the core bar of FIG. 3.

FIG. 5 is a lateral view showing the core bar of FIG. 4.

FIG. 6 is a plan view showing the inside of a modification of the corebar.

FIGS. 7A and 7B are plan views showing respectively the inside ofanother modification of the core bar.

FIGS. 8A and 8B are plan views showing respectively the inside of stillanother modification of the core bar.

FIG. 9 is a plan view showing the inside of a coupling body (1).

FIG. 10 is a lateral view of the coupling body (1).

FIG. 11 is a plan view showing the inside of a coupling body (2).

FIG. 12 is a lateral view of the coupling body (2).

FIG. 13 is a plan view showing the inside of a coupled state of the corebar and the coupling body in rubber.

FIG. 14 is a cross sectional view showing the coupled state of FIG. 13.

FIG. 15 is a cross sectional view showing the rubber crawler accordingto a second example of the invention.

FIG. 16 is a cross sectional view showing the rubber crawler accordingto a third example of the invention.

FIG. 17 is a cross sectional view showing the rubber crawler accordingto a fourth example of the invention.

FIG. 18 is a cross sectional view showing the rubber crawler accordingto a fifth example of the invention.

FIG. 19 is a cross sectional view showing the rubber crawler accordingto a sixth example of the invention.

FIG. 20 is a plan view showing the inside of the rubber crawleraccording to a seventh example of the invention.

FIG. 21 is a plan view showing an outside of the rubber crawler of FIG.20.

DETAILED DESCRIPTION OF THE INVENTION

A rubber crawler of the present invention has core bars. The core barhas left and right wing portions where rubber is embedded. The left andright wing portions each have an edge portion which is a part of aclosed-loop opening. A coupling body with fitting portions is employed.Each of the fitting portion opens at both ends in an inward direction.The edge portions are coupled with the fitting portions to form thecoupling body and the core bars are connected with coupling bodies.

Because the edge portions in the left and right wing portions of thecore bar are coupled with the coupling body, which includes the edgeportions, the edge portions will not disengage from the coupling bodyeven if the tensile force is applied. Further, the core bars of theinvention can sequentially be set in the mold, which produces the rubbercrawler to couple the edge portions of the core bars with the couplingbody. Therefore, unlike the conventional example described above, thecoupling body is not required to fit from a lateral direction, and itsassemble process becomes simple.

In the case where the edge portions are the openings formed in the leftand right wing portions which are of the rubber embedding portion,because surroundings of the opening is in a closed state, the couplingbody will not disengage off from the lateral side.

A C-shaped coupling body has the shape appeared when viewed from alateral face. The C-shaped coupling body has the structure in which thefitting portions opened in the inward direction are provided at the bothends of the coupling body in the same sides with respect to the centralportion of the coupling body. An S-shaped coupling body has thestructure in which the fitting portions opened in the inward directionare provided at the both ends of the coupling body in the opposite sideswith respect to the central portion of the coupling body. Both theC-shaped coupling body and the S-shaped coupling body couple the edgeportions by fitting the edge portions into the fitting portions of thecoupling bodies.

In the invention, optimization of a relationship between the core barand the coupling body may be sought. Particularly, a structure whichprevents problems generated by external forces, when the rubber crawleris bent by a sprocket or an idler, or when reverse bending phenomenonoccurs in the case where the rubber crawler runs up on a protrusion of arunning surface, may be sought.

Therefore, assuming that the cross-sectional radius of the edge portionin the wing portion is set to R and the length from the deepest part ofthe fitting portion to an end of the fitting portion of the couplingbody is set to L, the edge portion will not disengage from the fittingportion of the coupling body when L is not lower than 1.5R. If L isexcessively longer, the fitting work will become difficult. In thissense, naturally, a limit of the length L exists.

When the lateral width of the edge portion of the core bar is set to Dand the width of the coupling body is set to A, A/D is not lower than0.7. D is not lower than A. When A/D is smaller than 0.7, the couplingbody might move in a lateral direction while the edge portion is fittedinto the coupling body, and the rigidity of the rubber crawlerdecreases. Namely, when A/D is not lower than 0.7, the side shift of thecoupling body in the widthwise direction is suppressed, the rigidity(twisting resistance) of the rubber crawler is ensured, running-offresistance and abrasive resistance (resistance to one-side abrasion) areimproved.

When the lateral width of the wing portion, which forms the edge portionis formed is set to B, in order to enhance the transverse rigidity ofthe rubber crawler, it is preferable that A/B is not lower than 0.3.When the lateral width of the core bar is set to C, in order to enhancethe transverse rigidity of the rubber crawler, it is preferable that A/Cis not lower than 0.1.

When the center interval between the pair of edge portions fitted intothe fitting portions of the coupling body is set to L₀ and the spacingof the rubber crawler is set to P in order to smoothly rotate the rubbercrawler, L₀/P may not be greater than 0.7 and L₀/P may not be lower than0.4.

In the C-shaped coupling body, the edge portions are fitted into thefitting portions, while the fitting portions face the outer radius sideof the rubber crawler, or while the fitting portions face the innerradius side of the rubber crawler. The inside of the rubber crawler iscompressed about the coupling body and the outside is subjected totensile force. In the case where the fitting portions face the outerradius side of the rubber crawler, since the end portions of the fittingportions face the outside, strain is concentrated on the end portions ofthe fitting portions when the outside is subjected to the tensile force.Therefore, sometimes a crack is generated from a starting point of theend portions outside the rubber, and the crack develops to decrease alife of the rubber crawler. The same phenomenon is generated in thefitting portions of the S-shaped coupling body.

The rubber rag is formed on the outer radius side of the rubber crawler.The rubber rag is formed at the position where the coupling body iscovered with the rubber rag, or between the coupling bodies at theposition where the wing portion of the core bar is covered with therubber rug. In order to eliminate the crack of the rubber, the rubberrag may be formed at the position where the coupling body is coveredwith the rubber rag. In the rubber crawler in which the fitting portionsof the coupling body are arranged so as to face the outside, the rubberrag at the position where the coupling body is covered with the rubberrag may be formed. In this case, the thickness of the rubber regionoutside the rubber crawler is increased with respect to the end portionsof the fitting portions of the coupling body, which allows the rubbercrack to be prevented.

When the rubber crawler of the invention is wound about the sprocket orthe like, the fitting portion of the coupling body is rotated about theedge portion. Because the rotation is repeated, the rubber near thefitting portion is always subjected to the strain due to the sheardistortion, and the crack caused mainly by degradation of the rubber islikely to occur. The rotational resistance of the rubber crawler isincreased due to shear resistance of the rubber, which causes energyloss.

In consideration of the adverse effects caused by the shear resistanceon the rubber, the rubber may be removed in the region where the cracktends to occur. Along with this, in order to decrease the adverseaffection such as the generation of the rubber crack by the shearresistance and magnitude of the rotational resistance based on the shearresistance, the recess A may be provided at a predetermined position inthe rubber crawler.

Even if the above-described countermeasure is adopted, in winding therubber crawler about the sprocket, the distortion is concentrated on therubber elastic body in the width direction of the region in which thecoupling body is embedded, while the distortion is relatively small inthe region in which the coupling body is embedded because the couplingbody has the rigidity. The difference in the distortions is increasedbetween the coupling body and the rubber elastic body in the widthdirection out of the coupling body, which concentrates the strain causedby the repeated tension and the compressive distortion on the rubberelastic body in the region.

Therefore, in order to prevent the concentration of the strain caused bythe repeated compressive distortion, the recess B may be formed in therubber elastic body in the region apart from the coupling body in thewidth direction of the rubber crawler. As a result, the degradation ofthe rubber can be prevented and the durability of the rubber crawler canbe improved.

In FIG. 7 of Japanese Patent Laid-Open Publication No. 06-316281, theclosed-loop openings are formed in the left and right wing portions,which are of the rubber embedding portion. While Japanese PatentLaid-Open Publication No. 06-316281 improves the adhesion between thecore bar and the rubber which is of the base material of the rubbercrawler, no technical motive that the tensile materials are coupled byutilizing the opening. In this way, the Japanese Patent Laid-OpenPublication No. 06-316281 is completely different from the invention inthe structure.

EXAMPLES

Referring to the accompanying drawings, the present invention will bedescribed in detail below. FIG. 3 is a plan view showing an example ofthe core bar used for the rubber crawler of the invention when viewedfrom inside the rubber crawler, FIG. 4 is a front view showing the corebar. FIG. 5 is a lateral view showing the core bar.

In a core bar 10A, rectangular closed-loop openings 13 are formed inleft and right wing portions 11 and 12, which are embedded in the rubberrespectively. Edge portions 14 a, 14 b, and 14 c are formed to make arectangular closed loop around the closed-loop opening 13. Namely, ineach closed-loop opening 13, front and rear portions in a lengthwisedirection of the rubber crawler are preferably formed by the edgeportions 14 a and 14 b with substantially circular shaped crosssections, and closed by the edge portion 14 c. Each cross section of theedge portions 14 a and 14 b may have a substantially circular shape. Inthe present example, a pair of projections 15 and 16 is provided whilesandwiching a central portion 17, which becomes an engagement portionwith the sprocket. The projections 15 and 16 are arranged to have anappearance of being shifted from each other. Top surfaces of theprojections 15 and 16 become a running path of the rotating wheel (notshown) and have a function of preventing the rotating wheel from runningoff.

In the core bar 10A, the cross sections of the edge portions 14 a and 14b of the wing portions 11 and 12 are formed in the substantiallycircular shape having a radius R. A fitting portion of the coupling bodyis formed such that the edge portions 14 a and 14 b are fitted into thefitting portion. It is assumed that each lateral width of the edgeportions 14 a and 14 b is set to D. Both lateral widths of the wingportion 11 and 12 respectively in which the closed-loop opening 13 isformed are set to B. A width of the core bar 10A is set to D. Aninterval between centers of the pair of edge portions 14 a and 14 b isset to L₀.

FIG. 6 is a plan view showing another example of the core bar 10A.Similarly to FIG. 3, the closed-loop openings 13 are formed in the leftand right wing portions 11 and 12 respectively. The edge portions 14 aand 14 b are formed to make the rectangular closed loop around theclosed-loop opening 13. The core bar 10A has a projection 18 at thecentral portion. The core bar 10A is used for a type, which may becalled as inner drive type rubber crawler.

In the rectangular closed-loop openings 13 in which the edge portions 14a and 14 b are formed in the left and right wing portions 11 and 12, notonly one closed-loop opening 13 but also the plurality of closed-loopopenings 13 may be formed as shown in FIGS. 7A and 7B.

FIGS. 8A and 8B are plan views respectively showing still anotherexample of the core bar 10A. In FIG. 8A, each of the left and right wingportions 11 and 12 is divided into two portions in the lengthwisedirection of the rubber crawler. Each of the two portions appears tohave a shape of a tuning fork, and is to have the edge portions 14 a and14 b. Because the edge portions 14 a and 14 b are not closed,installation operation of the coupling body becomes easy. FIG. 8B showsstill another example. In the left and right wing portions 11 and 12 ofFIG. 8B, the edge portion 14 a or 14 b is formed in a rod-like body witha circular cross section.

FIG. 9 is a plan view showing an interior of an example of a belt-shapedcoupling body 20A of the invention. FIG. 10 is a lateral view showingthe coupling body 20A. Fitting portions 21 and 22 are formed at bothends of the coupling body 20A. The fitting portions 21 and 22 are formedon the same side with respect to the flat belt-shaped center portion 23of the coupling body 20A. Fitting ends 21 a and 22 b face the inside toappear to have a C-shape from outward appearance. The fitting portions21 and 22 are formed to have such a shape into which the edge portions14 a and 14 b of the core bar 10A are fitted. In the present example,the width of the coupling body 20A is slightly smaller than the width ofthe closed-loop opening 13 in the wing portion of the core bar. Theplurality of coupling bodies 20A may be lined up for use. Ends of thefitting ends 21 a and 22 b may be rounded in order to prevent theconcentration of strain of the rubber. This is also applicable to thelater-mentioned S-shaped coupling body.

In FIGS. 9 and 10, the reference letter L represents the length from thedeepest part of the fitting portion of the coupling body to the end ofthe fitting portion. The reference letter A represents the width of thecoupling body. The width L and the width A are prepared according to theabove-described conditions in relation to the size of regions of thecore bar.

FIG. 11 is a plan view showing the inside of an example of a belt-shapedcoupling body 20B of the invention. FIG. 12 is a side view of thecoupling body 20B. The fitting portions 21 and 22 are formed at bothends of the coupling body 20B. The fitting portions 21 and 22 are formedon the opposite sides with respect to the flat belt-shaped centerportion 23 of the coupling body 20B. The fitting ends 21 a and 22 b areopened while facing to the inside of the coupling body 20B. The couplingbody 20B is substantially formed in an S-shape when viewed from the sideface. The fitting portions 21 and 22 are formed to have such a shapeinto which the edge portions 14 a and 14 b of the core bar 10B arefitted. In the present example, the width of the coupling body 20B isslightly smaller than the width of the closed-loop opening 13 in thewing portion of the core bar. The two-divided coupling bodies 20B may beused. In this case, the edge portions 14 a and 14 b may be fitted intothe fitting portions 21 and 22 and the fitting portions 21 and 22 may beinversely arranged such that the central portions of the pair ofcoupling bodies 20B intersect with each other. In the case where thecentral portion 23 is intersected with each other and embedded in therubber crawler, the strength remarkably improves as a counter-tensionmember.

FIG. 13 is a plan view showing the inside of a coupled state of the corebar 10A and the coupling body 20A embedded in a rubber 30. FIG. 14 is across sectional view showing the coupled state of FIG. 13. The fittingportions 21 and 22 formed at the both ends of the coupling body 20A arecoupled with the edge portions 14 a and 14 b constituting theclosed-loop opening 13 of the core bar 10. After this coupling, the edgeportions 14 a and 14 b are included into the portions 21 and 22, and theedge portions 14 a and 14 b are included inside the fitting portions 21and 22. Thus, the wing portions 11 and 12 of the core bars 20A embeddedin the rubbers 30 are sequentially coupled, and the core bars 10A arecoupled with each other to have the edge portions 14 a and 14 b insidethe fitting portions 21 and 22. As a result, the coupling body 20A willnot disengage easily. As described above, a smaller width of thecoupling body 20A may be employed to have the edge portions 14 a and 14b inside by coupling the plurality of coupling bodies.

Because the fitting between the edge portions 14 a and 14 b of the corebar 10A and the coupling body 20A can be performed only by slightlybringing one of the core bars 10A near to the other, work process issimple. Further, because the core bars 10A can be coupled with thecoupling body 20A after the core bars 10A are set in the mold, workingefficiency is extremely increased. In this case, in the rubber crawler,the fitting portions 21 and 22 of the coupling body 20A face the innerradius side. It is also possible that the fitting portions 21 and 22 ofthe coupling body 20A face the outer radius side. Sometimes a syntheticreinforcement material or a metal fiber material is embedded across thefitting ends 21 a and 22 b of the coupling body 20A. One or a pluralityof sheets of reinforcement materials formed like in a reed screen orcanvas may be used.

As shown in FIG. 14, in the invention, rags 40 are formed on the outersurface of the rubber crawler. The rag 40 is formed between the core bar10A while the end portions of the fitting portions 21 and 22 of thecoupling body 20A are covered with the base portion of the rag 40. Athickness of the rubber is increased by forming the rag 40 outside thefitting portion 21 and 22, in which the crack is most easily generated,and the rubber strain concentrated on the ends of the fitting portions21 and 22 is absorbed by the thickness of the rubber. As a result, thegeneration of the crack is substantially eliminated. Sometimes thesynthetic reinforcement material or the metal fiber material is embeddedacross the fitting ends 21 a and 22 b of the coupling body 20A. One ormore than two sheets of reinforcement materials formed like in a reedscreen or canvas may be used. FIG. 15 shows a second example of theinvention in which the rag 40 is formed corresponding to the core bar10A.

FIG. 16 shows a third example of the invention in which the fittingportions 21 and 22 of the coupling body 20A face the outer radius sideof the rubber crawler. The inside of the rubber crawler is compressedabout the coupling body 20A and the outside of the rubber crawler issubjected to the tensile stress. In a conventional rubber crawler, therag 40 is formed on the outer surface corresponding to the core bar 10A,and sometimes the crack a may be generated from a starting point of thefitting ends 21 a and 22 b of the coupling body 20A outside the rubber.The crack a may develop and affect the life of the rubber crawler. Thisphenomenon may similarly occur in the S-shaped coupling body.

FIG. 17 shows a fourth example of the invention which is to eliminatethe occurrence of the crack a of the rubber. In the rubber crawler inwhich the fitting portions 21 and 22 of the coupling body 20A arearranged on the outside, the thickness of the rubber is increased on theoutside corresponding to the fitting portions 21 and 22 of the couplingbody 20A. The rag is formed at the position where the fitting portions21 and 22 are to be covered. Namely, because the rag 40 is formed tocover the coupling body 20A in accordance with the fitting portions 21and 22 where the crack a may be generated in the rubber, the thicknessof the rubber corresponding to the fitting portions 21 and 22 isincreased. Accordingly, the strain applied to the rubber is dispersedand absorbed, which largely decreases the generation of the crack. Thebase portion of the rag 40 is at least covered with respect to thefitting portions 21 and 22 of the coupling body 20A. Because one of thefitting portions of the S-shaped coupling body is in the same state asthe C-shaped coupling body 20A, the rag is formed at the position whereone of the fitting portions is to be covered.

FIG. 18 is a cross sectional view showing a fifth example of the rubbercrawler of the invention when the second coupling body 20B is used. Inthe coupling body 20B, the fitting portions 21 and 22 are formed in thelengthwise direction of the rubber crawler are symmetric with respect tothe central portion of the coupling body 20B. The rag 40 is formed onthe outer surface of the rubber crawler to cover the coupling body 20B.As described regarding the C-shaped coupling body, the invention is notlimited to the fourth example. The rag 40 may be formed between thecoupling bodies 20B, i.e. the rag 40 is formed to cover the wingportions of the core body.

FIG. 19 is a cross sectional view showing a sixth example about amodification of the rubber crawler of the invention. When the rubbercrawler is wound about the sprocket or the idler, or in order to followa rough road surface, the fitting portions 21 and 22 of the couplingbody 20A are rotated about the edge portions 14 a and 14 b. In thiscase, the rubber in the region where the rubber is sandwiched betweenthe fitting portions 21 and 22 of the adjacent coupling bodies 20A issubjected to a large strain.

In order to deal with this condition, a recess (A) 50 is prepared in theregion subject to such a strain in this example. The recess (A) 50 isformed inside or outside the rubber crawler and usually the recess (A)50 is arranged in a line along the width direction of the rubbercrawler. In some cases, the recess 50 may be formed to go through therubber crawler. Even if the rotating action is applied to a portionbetween the fitting portions 21 and 22 of the coupling body 20A and theedge portions 14 a and 14 b, a large shear strain will not occur in thespecific region. In addition, the winding resistance of the rubbercrawler is lowered. In the C-shaped coupling body 20A, forming anunillustrated recess in the rubber between the fitting portions 21 and22 is effective for the shear strain. Sometimes the syntheticreinforcement material or the metal fiber material may be embeddedacross the fitting ends 21 a and 22 b of the coupling body 20A. One ormore sheets of reinforcement materials formed in the reed screen or thecanvas may be used.

As described above, when the edge portions 14 a and 14 b are fitted intothe plurality of C-shaped coupling bodies 20A, or when the edge portions14 a and 14 b are fitted into the C-shaped coupling body while thecoupling body is arranged inside out, the same effect is obtained byforming the recess (A) 50 in the rubber in the region where the shearstrain is generated. Even if the rag 40 is formed at the position wherethe rag 40 faces not the coupling body 20A but the core bar 10A, thesame effect is also obtained.

FIG. 20 is a plan view showing the inner radius side of a seventhexample in which the rubber crawler of the invention is furtherimproved, and FIG. 21 is a plan view showing the outer radius side ofthe rubber crawler shown in FIG. 20. The reference numeral 30 representsa rubber elastic body. The pair of projections 15 and 15 projecting fromthe inner radius surface of the rubber elastic body 30 is provided onthe core bar 10A, and the wing portions 11 and 12 are provided on theleft and right sides of the projections 15 and 15. The wing portions 11and 12 are embedded in the rubber elastic body 30. The core bar 10Aequivalent to the core bar shown in FIGS. 3 to 5 is used. The componentsare coupled with the C-shaped coupling body 20A.

When the rubber crawler is wound about the idler or the sprocket, thedistortion is concentrated on the rubber portion in the width direction,in which the coupling body 20A is not embedded, while the coupling body20A which is of a rigid body never bends. The regions on which thestrain is concentrated by the repeated distortion are an A, portion andan A₂ portion (shown by oblique lines) in the inner radius surface andan A₃ portion and an A₄ portion (shown by oblique lines) in the outerradius surface corresponding to the coupling body 20A of the rubberelastic body 30. Namely, the region on which the strain is concentratedis the rubber portion located on left and right sides in the widthdirection of the coupling body 20A. Further, when the rubber crawler iswound about the sprocket or the like, the rubber crawler does not rotatesmoothly or rotates badly, the rotational resistance also increases, andthe durability of the rubber crawler is also largely affected.

In order to deal with this, in the rubber of the region on which thestrain is concentrated, it is necessary to form the structure in whichthe repeated distortion will be as smooth as possible. The presentexample is a modification for this necessity. The thickness of therubber elastic body in the regions of A, to A₄ is formed to lower theresistance against the repeated distortion. Specifically, a recess (B)60 is formed in order to decrease the thickness of the rubber in theregions A, to A₄.

The recess (B) 60 may be provided on the outside of A, in the widthdirection of the coupling body 20 a in the inner radius surface of therubber elastic body 30. The recess (B) 60 may be provided in otherregions. In some cases, The recesses (B) 60 may be formed in theabove-described places.

INDUSTRIAL APPLICABILITY

The present invention has the configurations as described above. Thetensile material (steel cord) body, which has been regardedindispensable, is omitted in the invention. In this way, the inventionprovides a rubber crawler, which can serve new applications.

1. A rubber crawler comprising: core bars which are embedded at constantintervals in a lengthwise direction of the rubber crawler, wherein apair of edge portions is formed in each of left and right wing portionswhich are of a rubber embedding portion of a core bar, the edge portionsof the adjacent core bars are coupled with each other by fitting theedge portions into fitting portions with a coupling body including thefitting portions in which both ends are opened in an inward direction,and the coupling body is caused to be a tensile material.
 2. The rubbercrawler of claim 1, wherein the pair of edge portions is made by forminga closed-loop opening in the left and right wing portions of the corebar.
 3. The rubber crawler of claim 1, wherein the pair of edge portionsis made by forming a tuning fork shape in the left and right wingportions of the core bar.
 4. The rubber crawler of claim 1, wherein across section of the edge portion has a substantially circular shape. 5.The rubber crawler of claim 1, wherein the coupling body has a C-shapewhen viewed from a lateral face.
 6. The rubber crawler of claim 1,wherein the coupling body has an S-shape when viewed from a side face.7. The rubber crawler of claim 5, wherein the coupling body is made of ametal material.
 8. The rubber crawler of claim 1, wherein the couplingbody is made of a plastic material.
 9. The rubber crawler of claim 5,wherein the edge portion has a circular cross section whose radius is R,and L≧1.5 R and A/D≧0.7 when a width of the edge portion is set to D, alength from the deepest portion of the fitting portion of the couplingportion to an end of the fitting portion is set to L, and a width of thecoupling body is set to A.
 10. The rubber crawler of claim 9, whereinA/B≧0.3 when a lateral width of the wing portion of the core bar is setto B.
 11. The rubber crawler of claim 9, wherein A/C≧0.1 when a lateralwidth of the core bar is set to C.
 12. The rubber crawler of claim 1,wherein 0.7≧LO/P≧0.4 when a center interval of the pair of edge portionsfitted into the fitting portions of the coupling body is set to Lo andeach interval of the rubber crawler is set to P.
 13. The rubber crawlerof claim 1, wherein rags are formed in an outer surface of the rubbercrawler located at a position g where the coupling body is covered. 14.The rubber crawler of claim 1, wherein a recess A is formed on an innerradius side and/or an outer radius side of the rubber crawler, and therecess A faces an end side in a lengthwise direction of the rubbercrawler of the coupling body.
 15. The rubber crawler of claim 14,wherein the recess A goes through from an inner surface to the outersurface of the rubber crawler.
 16. The rubber crawler of claim 14,wherein the recess A is formed along the edge portion in a widthdirection with respect to the rubber crawler of the coupling body. 17.The rubber crawler of claim 1, wherein a recess B is formed in a rubberelastic body out of the coupling body embedded in the width direction ofthe rubber crawler.
 18. The rubber crawler of claim 17, wherein therecess B is formed on an inside and/or an outside in the width directionof the coupling body.
 19. The rubber crawler of claim 17, wherein therecess B is formed on the inner radius side and/or the outer radius sideof the rubber elastic body.
 20. The rubber crawler of claim 17, whereinthe recesses B are formed in line in the width direction of the rubberelastic body.